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American Journal of Physical Medicine & Rehabilitation:
doi: 10.1097/PHM.0b013e3182241860
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Axial Low Back Pain in a Patient with a Mouse Face Sign on Bone Scan

Goldin, Michael S. MD; Mitra, Raj MD

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From the Division of Physical Medicine and Rehabilitation, Stanford University School of Medicine, Palo Alto, California.

Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.

All correspondence and requests for reprints should be addressed to: Raj Mitra, MD, Department of Orthopedic Surgery, Physical Medicine and Rehabilitation, Stanford Medicine Outpatient Center, 450 Broadway Street, Pavilion C, 4th Floor, MC 6342 Redwood City, CA 94063.

A 72-yr-old man with a medical history of prostate cancer presented with a chief complaint of gradually worsening axial low back pain over a 1-mo period. On physical examination, he was found to have intact motor strength in all lower limb myotomes, negative active root tension signs, and tenderness with palpation over the lower lumbar facet joints.

A lumbar spine magnetic resonance imaging (MRI) was performed and demonstrated a new enhancing sclerotic lesion of the T12 vertebral body concerning for blastic metastasis. A subsequent bone scan was obtained and revealed no evidence of osseous metastasis at T12. The bone scan did demonstrate a “clover leaf” or “mouse face” pattern at the L1 vertebral body. In addition, the bone scan demonstrated increased uptake in the left pelvis and acetabulum (Fig. 1). Findings were compatible with Paget disease of the left hemipelvis, as the contrast enhancement in the inferior aspect of the T12 vertebral body visualized on the MRI did not correlate with the increased uptake on the bone scan.

Figure 1
Figure 1
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Correlation between MRI and bone scans is helpful in discriminating Paget disease from a metastatic lesion. The distinction between Paget disease and blastic metastasis may be difficult. A key discriminating factor is that cortical uptake is evenly distributed in Paget disease (as demonstrated in the patient). Vertebral body metastasis also may be suggested by hypointensity of the T1-weighted signal, suggestive of loss of marrow fat.1

A scintigraphic clover pattern or mouse face in the lumbar spine has been associated with Paget disease but also may represent a metastatic lesion.2,3 Interestingly, our patient had findings consistent with metastasis on MRI at the T12 vertebral body but had a clover leaf sign at the L1 vertebral body (not at T12). The lack of correlation between the post gadolinium enhancement on the spine MRI and bone scan, in addition to the diffuse uptake in the left pelvis, was therefore more suggestive of Paget disease.

James Paget first described this disease as “osteitis deformans” in a case series of five patients with skeletal deformities in two or more bones, of which two patients eventually developed malignant bone tumors.4 Paget disease of the bone is characterized by abnormal bone remodeling and formation, which subsequently may lead to pain, fracture, and deformity. The disorder may affect any bone but has a predilection for the skull, hip, pelvis, legs, and spine.

Rehabilitation of patients with Paget disease is focused on maintenance and progression of functional range of motion. This patient underwent an extension-based spine therapy program with utilization of modalities (transcutaneous electric stimulation, superficial heat, and soft tissue mobilization). After 4 wks of physical therapy, the patient had moderate pain relief and increased both his standing and ambulation tolerance.

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REFERENCES

1. Sundaram M, Khanna G, El-Khoury GY: T1-weighted MR imaging for distinguishing large osteolysis of Paget’s disease for sarcomatous degeneration. Skeletal Radiol 2001; 30: 378–83

2. Reyes R, Peris P, Monegal A, et al.: Vertebral “clover” sign scintigraphic image in a vertebral metastasis misdiagnosed with Paget’s disease. Clin Rheumatol 2008; 27: 1585–6

3. Kim CK, Estrada WN, Lorberboym M, et al.: The “mouse face” appearance of the vertebrae in Paget’s disease. Clin Nucl Med 1997; 22: 104–8

4. Paget J: On a form of chronic inflammation of bones (osteitis deformans). Med Chir Trans 1877; 60: 37

© 2011 Lippincott Williams & Wilkins, Inc.

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